Aerodynamic Investigation of a Rotorcraft Lander Fixed to a Descending Capsule Backshell

NASA is funding a mission to explore the surface of Titan to investigate the terrain and chemical compositions that exist using a rotorcraft lander with four coaxial rotors (Dragonfly). On its entry into Titan, and at near surface atmospheric conditions, Dragonfly will exit a parachute supported backshell that has shed its protective heat shield. The aerodynamics of this condition are important for understanding the system dynamics. The goal of this paper is to highlight aerodynamic trends experienced by the Dragonfly lander and backshell combination during this phase of Entry, Descent, and Landing (EDL) using computational fluid dynamics (CFD). The paper first benchmarks the model using experimental measures of aerodynamic loads for similar backshells, bluff bodies, and rotors. From the results, it was found that all CFD models reflected the trends in their original experiments. The study then moves into a series of geometric and rotor settings and how they affect the aerodynamic character. In this process, we identify complex rotor-lander interactions across rotor configurations with no apparent benefit to backshell venting. Understanding of the complex flow has been important in developing solutions that target positive control authority of the system.